Instead, vaping is best thought of as a method of quitting smoking. As such, it can be a public-health tool. Because while e-cigarettes are not "safe," meaning zero risk, they're proving to be both dramatically safer than regular cigarettes and effective at helping people cut back on or quit smoking.

The public-health benefits of this latter achievement are huge. Regulators should keep those benefits in mind -- which means they should avoid heavy-handed rules that target vaping simply because the activity looks like smoking.

The strongest proponent of this view is Micheal Siegel, a professor at the Boston University School of Public Health. Siegel has impeccable credentials as an antismoking crusader. He has conducted tobacco research for 25 years and been a strong supporter of strict smoking and secondhand-smoke policies.

So, "when electronic cigarettes came to the U.S. about 2007, I was skeptical," Siegel wrote in January in a Wall Street Journal op-ed.

"My assumption was they were a ploy by the tobacco industry to hook more people into smoking under the guise of being a safer product. ... But as I talked to many e-cigarette users, known as 'vapers,' conducted research (Journal of Public Health Policy, 2011) and reviewed a growing body of scientific evidence, I became convinced that e-cigarettes have dramatic potential for reducing disease and death caused by smoking."

That attitude has strengthened since then, as the evidence has grown that e-cigarettes offer significant public-health benefits (through smoking reduction) at comparatively low risk.

Importantly, Siegel is not calling for the FDA to abandon its regulatory role. Just the opposite: The agency "should set uniform safety standards for e-cigarettes and 'vaping' products," he wrote.

"These standards should include childproof packaging, battery safety, quality-control standards for nicotine labeling and the production of e-liquids" and the like.

But heavily regulating e-cigarettes as tobacco products is overkill. Such rules mean fewer smokers would quit smoking -- and that would be a public-health loss.